Method for determining bearing play of exhaust-gas-turbocharger friction bearings

A method for evaluating exhaust-gas-turbocharger friction bearings, comprising the following method steps:

• accelerating a rotating body group of a turbocharger, the rotating body group comprising turbine wheel, compressor wheel, and shaft, said shaft supported by friction bearings, from standstill to a maximum rotational speed on a test bench and at the same time registering the vibration acceleration by means of a sensor;
• using the registered vibration acceleration to determine a constant-tone frequency associated with the friction bearings at at least one rotational speed of the turbocharger;
• looking up the determined constant-tone frequency on a diagram prepared by experimentally measuring constant-tone frequency and bearing-play of a number of friction bearings and showing a correlation between constant-tone frequency and bearing-play;
• and
• if the determined constant-tone frequency corresponds to a bearing play associated with an acoustically conspicuous noise when in vehicle, rejecting the exhaust-gas-turbocharger friction bearings.